The modern model of the atom is based on the work of

many scientists over a long period of time

one scientist over a short period of time

one scientist over a long period of time

many scientists over a short period of time

Which statement is true about the charges assigned to an electron and a proton?

An electron is negative and a proton is posi- tive.

Both an electron and a proton are positive.

An electron is positive and a proton is nega- tive.

Both an electron and a proton are negative.

In the wave-mechanical model, an orbital is a region of space in an atom where there is

a high probability of finding an electron

a high probability of finding a neutron

a circular path in which electrons are found

a circular path in which neutrons are found

Which statement describes a chemical property of iron?

Iron combines with oxygen to form rust.

Iron can be flattened into sheets.

Iron conducts electricity and heat.

Covalent bonds are formed when electrons are

transferred from one atom to another

Which type of molecule is CF4?

nonpolar, with a symmetrical distribution of charge

polar, with a symmetrical distribution of charge

polar, with an asymmetrical distribution of charge

nonpolar, with an asymmetrical distribution of charge

Which change occurs when a barium atom loses two electrons?

It becomes a positive ion and its radius decreases.

It becomes a negative ion and its radius decreases.

It becomes a negative ion and its radius increases.

It becomes a positive ion and its radius increases.

Conductivity in a metal results from the metal atoms having

highly mobile electrons in the valence shell

highly mobile protons in the nucleus

Helium is most likely to behave as an ideal gas when it is under

low pressure and high temperature

high pressure and high temperature

high pressure and low temperature

low pressure and low temperature

At STP, the element oxygen can exist as either O2 or O3 gas molecules. These two forms of the element have

different chemical and physical properties

the same chemical and physical properties

the same chemical properties and different physical properties

different chemical properties and the same physical properties

Which statement about a system at equilibrium is true?

The forward reaction rate is equal to the reverse reaction rate.

The forward reaction rate is less than the reverse reaction rate.

The forward reaction rate is greater than the reverse reaction rate.

The forward reaction rate stops and the reverse reaction rate continues.

A catalyst increases the rate of a chemical reaction by

lowering the activation energy of the reaction

lowering the potential energy of the products

raising the temperature of the reactants

raising the concentration of the reactants

Regents Chemistry Practice Test

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Questions: 50 | Attempts: 718 | Updated: Mar 22, 2023

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Questions and Answers

1.
1. The modern model of the atom is based on the work of
- A.
  
  One scientist over a short period of time
- B.
  
  One scientist over a long period of time
- C.
  
  Many scientists over a short period of time
- D.
  
  many scientists over a long period of time
Correct Answer
D. many scientists over a long period of time

Explanation
The modern model of the atom is based on the work of many scientists over a long period of time because the understanding of the atom has evolved and developed through the contributions of multiple researchers over many years. Different scientists have made significant discoveries and advancements in the field of atomic theory, building upon the work of their predecessors. This collaborative and cumulative effort has led to the development of the modern model of the atom, which incorporates the contributions and findings of many scientists over an extended period.

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2.
1. Which statement is true about the charges assigned to an electron and a proton?
- A.
  
  Both an electron and a proton are positive.
- B.
  
  An electron is positive and a proton is nega- tive.
- C.
  
  An electron is negative and a proton is posi- tive.
- D.
  
  Both an electron and a proton are negative.
Correct Answer
C. An electron is negative and a proton is posi- tive.

Explanation
An electron has a negative charge, while a proton has a positive charge. This is because electrons have a fundamental charge of -1, while protons have a fundamental charge of +1. Therefore, the statement "An electron is negative and a proton is positive" is true.

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3.
1. In the wave-mechanical model, an orbital is a region of space in an atom where there is
- A.
  
  A high probability of finding an electron
- B.
  
  A high probability of finding a neutron
- C.
  
  A circular path in which electrons are found
- D.
  
  A circular path in which neutrons are found
Correct Answer
A. A high probability of finding an electron

Explanation
An orbital in the wave-mechanical model represents the region of space around an atom where there is a high probability of finding an electron. It is not a circular path but rather a three-dimensional region that describes the electron's probable location. The wave-like nature of electrons allows them to exist in a cloud-like distribution within the orbital. Therefore, the correct answer is a high probability of finding an electron.

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4.
1. What is the charge of the nucleus in an atom of oxygen-17?
- A.
  
  0
- B.
  
  -2
- C.
  
  +8
- D.
  
  +17
Correct Answer
C. +8

Explanation
The charge of the nucleus in an atom of oxygen-17 is +8. This is because the atomic number of oxygen is 8, which represents the number of protons in the nucleus. The charge of the nucleus is determined by the number of protons, and since oxygen-17 has 8 protons, the charge is +8.

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5.

Which pair of symbols represents a metalloid and a noble gas?
- A.
  
  Si and Bi
- B.
  
  As and Ar
- C.
  
  Ge and Te
- D.
  
  Ne and Xe
Correct Answer
B. As and Ar

Explanation
As and Ar represent a metalloid (As) and a noble gas (Ar). Ar is a noble gas because it belongs to Group 18 of the periodic table and has a full outer electron shell, making it stable and unreactive. As is a metalloid because it has properties of both metals and nonmetals. It is located on the staircase line on the periodic table, separating the metals from the nonmetals.

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6.

Which statement describes a chemical property of iron?
- A.
  
  Iron can be flattened into sheets.
- B.
  
  Iron conducts electricity and heat.
- C.
  
  Iron combines with oxygen to form rust.
- D.
  
  Iron can be drawn into a wire.
Correct Answer
C. Iron combines with oxygen to form rust.

Explanation
The statement "Iron combines with oxygen to form rust" describes a chemical property of iron. Chemical properties describe how a substance interacts with other substances to form new substances. In this case, iron reacts with oxygen in the presence of moisture to form a new substance called rust. This reaction is a chemical property of iron because it involves a change in the composition and structure of the iron atoms.

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7.

Given the reaction: N2(g) + 3 H2(g) <-> 2 NH3(g) What is the mole-to-mole ratio between nitro- gen gas and hydrogen gas?
- A.
  
  1:2
- B.
  
  1:3
- C.
  
  2:2
- D.
  
  2:3
Correct Answer
B. 1:3

Explanation
The mole-to-mole ratio between nitrogen gas (N2) and hydrogen gas (H2) in the given reaction is 1:3. This means that for every 1 mole of nitrogen gas, there are 3 moles of hydrogen gas involved in the reaction.

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8.

What is the percent by mass of oxygen in propanal, CH3CH2CHO?
- A.
  
  10.0%
- B.
  
  27.6%
- C.
  
  38.1%
- D.
  
  62.1%
Correct Answer
B. 27.6%

Explanation
The percent by mass of oxygen in propanal, CH3CH2CHO, can be calculated by finding the molar mass of oxygen in the compound and dividing it by the molar mass of the entire compound. The molar mass of oxygen is 16 g/mol, and the molar mass of propanal is 58 g/mol. Dividing 16 g/mol by 58 g/mol and multiplying by 100 gives a result of approximately 27.6%.

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9.

Covalent bonds are formed when electrons are
- A.
  
  Transferred from one atom to another
- B.
  
  Captured by the nucleus
- C.
  
  Mobile within a metal
- D.
  
  Shared between two atoms
Correct Answer
D. Shared between two atoms

Explanation
Covalent bonds are formed when electrons are shared between two atoms. In a covalent bond, the atoms involved share their outermost electrons in order to achieve a stable electron configuration. This sharing of electrons allows both atoms to fill their outermost energy levels and form a strong bond. Unlike in ionic bonds where electrons are transferred from one atom to another, in covalent bonds, the electrons are shared, resulting in a balanced distribution of electron density between the atoms.

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10.

Which type of molecule is CF4?
- A.
  
  Polar, with a symmetrical distribution of charge
- B.
  
  Polar, with an asymmetrical distribution of charge
- C.
  
  Nonpolar, with a symmetrical distribution of charge
- D.
  
  Nonpolar, with an asymmetrical distribution of charge
Correct Answer
C. Nonpolar, with a symmetrical distribution of charge

Explanation
CF4 is a nonpolar molecule with a symmetrical distribution of charge. This is because the four fluorine atoms surrounding the central carbon atom are arranged in a tetrahedral shape, with the bond dipoles canceling each other out. As a result, there is no net dipole moment in the molecule, making it nonpolar.

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11.

Which change occurs when a barium atom loses two electrons?
- A.
  
  It becomes a negative ion and its radius decreases.
- B.
  
  It becomes a negative ion and its radius increases.
- C.
  
  It becomes a positive ion and its radius decreases.
- D.
  
  It becomes a positive ion and its radius increases.
Correct Answer
C. It becomes a positive ion and its radius decreases.

Explanation
When a barium atom loses two electrons, it becomes a positive ion. This is because it now has more protons than electrons, giving it a net positive charge. The loss of electrons also leads to a decrease in the size of the ion's electron cloud, which results in a decrease in its radius.

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12.
1. Which of these elements has the least attraction for electrons in a chemical bond?
- A.
  
  Oxygen
- B.
  
  Fluorine
- C.
  
  Nitrogen
- D.
  
  Chlorine
Correct Answer
C. Nitrogen

Explanation
Nitrogen has the least attraction for electrons in a chemical bond compared to oxygen, fluorine, and chlorine. This is because nitrogen has a lower electronegativity value, indicating a weaker ability to attract electrons towards itself in a bond. Oxygen, fluorine, and chlorine have higher electronegativity values, making them more likely to attract electrons in a chemical bond.

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13.
1. Conductivity in a metal results from the metal atoms having
- A.
  
  High electronegativity
- B.
  
  High ionization energy
- C.
  
  highly mobile protons in the nucleus
- D.
  
  highly mobile electrons in the valence shell
Correct Answer
D. highly mobile electrons in the valence shell

Explanation
Conductivity in a metal is due to the presence of highly mobile electrons in the valence shell. These valence electrons are not tightly bound to the metal atoms and are able to move freely throughout the metal lattice. As a result, they can carry an electric current, making metals good conductors of electricity. Electronegativity and ionization energy are not directly related to conductivity in metals.

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14.
1. Recovering the salt from a mixture of salt and water could best be accomplished by
- A.
  
  Evaporation
- B.
  
  Filtration
- C.
  
  Paper chromatography
- D.
  
  Density determination
Correct Answer
A. Evaporation

Explanation
Evaporation is the process of converting a liquid into a gas by heating it. In the case of a mixture of salt and water, evaporation can be used to separate the two components. When the mixture is heated, the water will evaporate and turn into vapor, leaving behind the salt. The vapor can then be condensed back into liquid form, leaving behind pure water. This method is effective for separating salt from water because salt does not evaporate at the same temperature as water, allowing for the separation of the two substances.

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15.
1. The average kinetic energy of water molecules is greatest in which of these samples?
- A.
  
  10 g of water at 35°C
- B.
  
  10 g of water at 55°C
- C.
  
  100 g of water at 25°C
- D.
  
  100 g of water at 45°C
Correct Answer
B. 10 g of water at 55°C

Explanation
The average kinetic energy of water molecules is directly proportional to temperature. As the temperature increases, the kinetic energy of the molecules also increases. Therefore, the sample with 10 g of water at 55°C will have the greatest average kinetic energy of water molecules among the given options.

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16.
1. Helium is most likely to behave as an ideal gas when it is under
- A.
  
  High pressure and high temperature
- B.
  
  High pressure and low temperature
- C.
  
  Low pressure and high temperature
- D.
  
  Low pressure and low temperature
Correct Answer
C. Low pressure and high temperature

Explanation
Helium is most likely to behave as an ideal gas when it is under low pressure and high temperature. At low pressure, the gas particles are far apart, allowing them to move freely and exhibit ideal gas behavior. High temperature increases the kinetic energy of the gas particles, causing them to move faster and collide more frequently. These conditions promote the ideal gas behavior where there are no intermolecular forces and the volume of the gas particles is negligible compared to the total volume of the gas.

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17.
1. At STP, the element oxygen can exist as either O2 or O3 gas molecules. These two forms of the element have
- A.
  
  The same chemical and physical properties
- B.
  
  The same chemical properties and different physical properties
- C.
  
  Different chemical properties and the same physical properties
- D.
  
  Different chemical and physical properties
Correct Answer
D. Different chemical and pHysical properties

Explanation
Oxygen can exist as either O2 or O3 gas molecules at STP. These two forms have different chemical properties because O2 is a diatomic molecule, while O3 is a triatomic molecule. O2 is stable and non-reactive, while O3 is highly reactive and unstable. In terms of physical properties, O2 is a colorless and odorless gas, while O3 is a pale blue gas with a distinct odor. Therefore, O2 and O3 have both different chemical and physical properties.

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18.

Which sample contains particles in a rigid, fixed, geometric pattern?
- A.
  
  CO2 (aq)
- B.
  
  HCl (g)
- C.
  
  H2O (l)
- D.
  
  KCl (s)
Correct Answer
D. KCl (s)

Explanation
KCl (s) is the correct answer because it is in the solid state, which means that its particles are tightly packed and arranged in a rigid, fixed, geometric pattern. In contrast, CO2 (aq) is in the aqueous state, where the particles are dispersed and not in a fixed pattern. HCl (g) is in the gaseous state, where the particles are highly mobile and not fixed in a pattern. H2O (l) is in the liquid state, where the particles are close together but not in a rigid, fixed pattern.

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19.

Given the reaction at 25°C: Zn(s) + 2 HCl(aq) → ZnCl2(aq) + H2(g) The rate of this reaction can be increased by using 5.0 grams of powdered zinc instead of a 5.0-gram strip of zinc because the powdered zinc has
- A.
  
  Lower kinetic energy
- B.
  
  Lower concentration
- C.
  
  More surface area
- D.
  
  More zinc atoms
Correct Answer
C. More surface area

Explanation
The rate of a reaction is often dependent on the surface area of the reactants. By using powdered zinc instead of a solid strip, the zinc is in smaller particles, resulting in a larger surface area. This increased surface area allows for more zinc atoms to come into contact with the hydrochloric acid, leading to more frequent and effective collisions between the reactants. As a result, the rate of the reaction is increased.

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20.

Which statement about a system at equilibrium is true?
- A.
  
  The forward reaction rate is less than the reverse reaction rate.
- B.
  
  The forward reaction rate is greater than the reverse reaction rate.
- C.
  
  The forward reaction rate is equal to the reverse reaction rate.
- D.
  
  The forward reaction rate stops and the reverse reaction rate continues.
Correct Answer
C. The forward reaction rate is equal to the reverse reaction rate.

Explanation
At equilibrium, the forward and reverse reaction rates are equal. This means that the rate at which products are formed in the forward reaction is the same as the rate at which reactants are formed in the reverse reaction. This balance between the two rates ensures that the concentrations of reactants and products remain constant over time, resulting in a stable system.

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21.

A catalyst increases the rate of a chemical reaction by
- A.
  
  Lowering the activation energy of the reaction
- B.
  
  Lowering the potential energy of the products
- C.
  
  Raising the temperature of the reactants
- D.
  
  Raising the concentration of the reactants
Correct Answer
A. Lowering the activation energy of the reaction

Explanation
A catalyst increases the rate of a chemical reaction by lowering the activation energy of the reaction. Activation energy is the energy required for a reaction to occur. By lowering this energy barrier, a catalyst allows the reaction to proceed more easily and quickly. It does not affect the potential energy of the products, the temperature of the reactants, or the concentration of the reactants.

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22.

Which element must be present in an organic compound?
- A.
  
  Hydrogen
- B.
  
  Oxygen
- C.
  
  Carbon
- D.
  
  Nitrogen
Correct Answer
C. Carbon

Explanation
Carbon must be present in an organic compound because organic compounds are defined as compounds that contain carbon atoms bonded to hydrogen atoms. Carbon is unique in its ability to form stable covalent bonds with other carbon atoms and with a variety of other elements, allowing for the formation of complex and diverse organic molecules. Without carbon, a compound cannot be classified as organic.

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23.

Which compound is a saturated hydrocarbon?
- A.
  
  Hexane
- B.
  
  Hexene
- C.
  
  Hexanol
- D.
  
  Hexanal
Correct Answer
A. Hexane

Explanation
Hexane is a saturated hydrocarbon because it contains only single bonds between carbon atoms, meaning that each carbon atom is bonded to the maximum number of hydrogen atoms possible. This results in a molecule that is "saturated" with hydrogen atoms. Hexene, hexanol, and hexanal all contain double or triple bonds between carbon atoms, making them unsaturated hydrocarbons.

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24.
1. Which of these compounds has chemical prop- erties most similar to the chemical properties of ethanoic acid?
- A.
  
  C3H7COOH
- B.
  
  C2H5OH
- C.
  
  C2H5COOC2H5
- D.
  
  C2H5OC2H5
Correct Answer
A. C3H7COOH

Explanation
C3H7COOH has chemical properties most similar to ethanoic acid because it is a carboxylic acid just like ethanoic acid. Both compounds have a carboxyl group (COOH) which gives them similar chemical properties such as acidity and the ability to form hydrogen bonds. The other compounds listed are different types of compounds - C2H5OH is an alcohol, C2H5COOC2H5 is an ester, and C2H5OC2H5 is an ether - and do not have the same chemical properties as ethanoic acid.

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25.
1. Given the reaction that occurs in an electrochemical cell: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s) During this reaction, the oxidation number of Zn changes from
- A.
  
  0 to +2
- B.
  
  0 to -2
- C.
  
  +2 to 0
- D.
  
  -2 to 0
Correct Answer
A. 0 to +2

Explanation
In the given reaction, Zn(s) is oxidized to Zn2+ ions, which have a +2 oxidation state. Since the oxidation state of Zn changes from 0 to +2, the correct answer is 0 to +2.

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26.

This reaction is an example of
- A.
  
  Fermentation
- B.
  
  Saponification
- C.
  
  Hydrogenation
- D.
  
  Esterification
Correct Answer
D. Esterification

Explanation
This reaction is an example of esterification because it involves the formation of an ester. Esterification is a chemical reaction between an alcohol and an acid, resulting in the formation of an ester and water. In this reaction, an ester is being formed, but we don't have enough information to determine the specific alcohol and acid involved.

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1
0
27.

A voltaic cell spontaneously converts
- A.
  
  Electrical to chemical energy
- B.
  
  Chemical to electrical energy
- C.
  
  Electrical to nuclear energy
- D.
  
  Nuclear to electrical energy
Correct Answer
B. Chemical to electrical energy

Explanation
A voltaic cell is an electrochemical cell that converts chemical energy into electrical energy through a spontaneous redox reaction. In this type of cell, chemical reactions occur at the electrodes, generating a flow of electrons and producing an electric current. Therefore, the correct answer is "chemical to electrical energy."

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28.
1. Which pair of formulas represents two compounds that are electrolytes?
- A.
  
  HCl and CH3OH
- B.
  
  HCl and NaOH
- C.
  
  C5H12 and CH3OH
- D.
  
  C5H12 and NaOH
Correct Answer
B. HCl and NaOH

Explanation
HCl and NaOH are both strong acids and bases, respectively, which dissociate completely in water to form ions. This means that they are able to conduct electricity and are therefore electrolytes. On the other hand, CH3OH and C5H12 are organic compounds that do not dissociate into ions in water, so they are not electrolytes.

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1
0
29.
1. Hydrogen chloride, HCl, is classified as an Arrhenius acid because it produces
- A.
  
  H+ ions in aqueous solution
- B.
  
  Cl– ions in aqueous solution
- C.
  
  OH– ions in aqueous solution
- D.
  
  NH4+ ions in aqueous solution
Correct Answer
A. H+ ions in aqueous solution

Explanation
Hydrogen chloride, HCl, is classified as an Arrhenius acid because it produces H+ ions in aqueous solution. This is a characteristic of Arrhenius acids, which are substances that dissociate in water to produce H+ ions. In the case of HCl, it dissociates into H+ and Cl- ions when dissolved in water. The presence of H+ ions in the solution makes it acidic.

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30.

Which compound could serve as a reactant in a neutralization reaction?
- A.
  
  NaCl
- B.
  
  KOH
- C.
  
  CH3OH
- D.
  
  CH3CHO
Correct Answer
B. KOH

Explanation
KOH can serve as a reactant in a neutralization reaction because it is a strong base. In a neutralization reaction, an acid reacts with a base to form a salt and water. KOH is a base because it dissociates in water to release hydroxide ions (OH-) which can then react with hydrogen ions (H+) from an acid to form water. NaCl, CH3OH, and CH3CHO are not bases and therefore cannot serve as reactants in a neutralization reaction.

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31.

Which of these particles has the greatest mass?
- A.
  
  Alpha
- B.
  
  Beta
- C.
  
  Neutron
- D.
  
  Positron
Correct Answer
A. AlpHa

Explanation
The alpha particle has the greatest mass among the given particles. An alpha particle is composed of two protons and two neutrons, making it a helium nucleus. It is relatively large and heavy compared to the other particles listed, such as the beta particle (electron or positron) which has negligible mass, and the neutron which is slightly heavier than a proton. Therefore, the alpha particle has the greatest mass.

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32.

In a nuclear fusion reaction, the mass of the products is
- A.
  
  Less than the mass of the reactants because some of the mass has been converted to energy
- B.
  
  Less than the mass of the reactants because some of the energy has been converted to mass
- C.
  
  More than the mass of the reactants because some of the mass has been converted to energy
- D.
  
  More than the mass of the reactants because some of the energy has been converted to mass
Correct Answer
C. More than the mass of the reactants because some of the mass has been converted to energy

Explanation
In a nuclear fusion reaction, some of the mass is converted to energy according to Einstein's mass-energy equivalence principle (E=mc²). This means that the total mass of the products is greater than the mass of the reactants, as some of the mass has been converted into energy.

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33.

Which of these types of radiation has the greatest penetrating power?
- A.
  
  Alpha
- B.
  
  Beta
- C.
  
  Gamma
- D.
  
  Positron
Correct Answer
C. Gamma

Explanation
Gamma radiation has the greatest penetrating power among the given options. Gamma rays are high-energy electromagnetic waves that can easily pass through most materials, including thick layers of lead and concrete. They have no mass or charge, allowing them to travel long distances and penetrate deep into matter. In comparison, alpha and beta particles are larger and have charges, making them less penetrating. Positrons, which are antimatter particles, also have limited penetrating power. Therefore, gamma radiation is the correct answer.

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34.

How many electrons are contained in an Au3+ ion?
- A.
  
  76
- B.
  
  79
- C.
  
  82
- D.
  
  197
Correct Answer
A. 76

Explanation
An Au3+ ion refers to a gold ion with a charge of +3. The atomic number of gold (Au) is 79, which means it has 79 electrons in a neutral state. However, since the ion has a +3 charge, it has lost 3 electrons. Therefore, the number of electrons in an Au3+ ion is 79 - 3 = 76.

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35.
1. Which electron configuration represents the electrons of an atom in an excited state?
- A.
  
  2-4
- B.
  
  2-6
- C.
  
  2-7-2
- D.
  
  2-8-2
Correct Answer
C. 2-7-2

Explanation
The electron configuration 2-7-2 represents the electrons of an atom in an excited state. In the ground state, the electron configuration of an atom follows the Aufbau principle, which states that electrons fill the lowest energy levels first. However, in an excited state, electrons can be promoted to higher energy levels by absorbing energy. In this case, the atom has two electrons in the first energy level (2), seven electrons in the second energy level (7), and two electrons in the third energy level (2), indicating that it is in an excited state.

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36.
- A.
  
  Three fewer neutrons
- B.
  
  Three fewer valence electrons
- C.
  
  Three more neutrons
- D.
  
  Three more valence electrons
Correct Answer
B. Three fewer valence electrons
37.
1. Element X is a solid that is brittle, lacks luster, and has six valence electrons. In which group on the Periodic Table would element X be found?
- A.
  
  1
- B.
  
  2
- C.
  
  15
- D.
  
  16
Correct Answer
D. 16

Explanation
Element X is a solid that is brittle and lacks luster, indicating that it is a nonmetal. It has six valence electrons, which means it belongs to Group 16 on the Periodic Table. Group 16, also known as the Oxygen Group or the Chalcogens, consists of nonmetals such as oxygen, sulfur, and selenium. These elements typically have six valence electrons and exhibit similar chemical properties. Therefore, element X would be found in Group 16 on the Periodic Table.

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38.
1. What is the empirical formula for the compound C6H12O6?
- A.
  
  CH2O
- B.
  
  C2H4O2
- C.
  
  C3H6O3
- D.
  
  C6H12O6
Correct Answer
A. CH2O

Explanation
The empirical formula represents the simplest ratio of elements in a compound. In the case of C6H12O6, the ratio of carbon (C), hydrogen (H), and oxygen (O) atoms is 1:2:1. Therefore, the empirical formula for C6H12O6 is CH2O.

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39.

The bonds between hydrogen and oxygen in a water molecule are classified as
- A.
  
  Polar covalent
- B.
  
  Nonpolar covalent
- C.
  
  Ionic
- D.
  
  Metallic
Correct Answer
A. Polar covalent

Explanation
The bonds between hydrogen and oxygen in a water molecule are classified as polar covalent because there is a significant difference in electronegativity between the two atoms. Oxygen is more electronegative than hydrogen, causing it to attract the shared electrons more strongly. This results in a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms, creating a polar molecule.

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0
1
40.
- A.
  
  AB
- B.
  
  BC
- C.
  
  CD
- D.
  
  EF
Correct Answer
B. BC
41.

Using your knowledge of chemistry and the information in Reference Table H, which statement concerning propanone and water at 50°C is true?
- A.
  
  Propanone has a higher vapor pressure and stronger intermolecular forces than water.
- B.
  
  Propanone has a higher vapor pressure and weaker intermolecular forces than water.
- C.
  
  Propanone has a lower vapor pressure and stronger intermolecular forces than water.
- D.
  
  Propanone has a lower vapor pressure and weaker intermolecular forces than water.
Correct Answer
B. Propanone has a higher vapor pressure and weaker intermolecular forces than water.

Explanation
Propanone has a higher vapor pressure and weaker intermolecular forces than water because at 50°C, propanone molecules have a higher tendency to escape from the liquid phase and enter the gas phase compared to water. This is because propanone has weaker intermolecular forces, which are the forces of attraction between molecules, compared to water. Weaker intermolecular forces result in a higher vapor pressure. Water, on the other hand, has stronger intermolecular forces, which leads to a lower vapor pressure at the same temperature.

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42.

A solution that is at equilibrium must be
- A.
  
  Concentrated
- B.
  
  Dilute
- C.
  
  Saturated
- D.
  
  Unsaturated
Correct Answer
C. Saturated

Explanation
A solution that is at equilibrium must be saturated. When a solution is saturated, it means that it contains the maximum amount of solute that can be dissolved in the solvent at a given temperature. At equilibrium, the rate of dissolution of solute is equal to the rate of precipitation, resulting in a stable concentration of solute in the solution. Concentrated and dilute solutions refer to the amount of solute present relative to the amount of solvent, while unsaturated solutions can dissolve more solute and are not at equilibrium.

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43.
- A.
  
  Increasing the concentration of NO (g)
- B.
  
  Increasing the concentration of N2 (g)
- C.
  
  Decreasing the reaction temperature
- D.
  
  Decreasing the reaction pressure
Correct Answer
B. Increasing the concentration of N2 (g)
44.
1. Which 10-milliliter sample of water has the greatest degree of disorder?
- A.
  
  H2O (g) at 120°C
- B.
  
  H2O (l) at 80°C
- C.
  
  H2O (l) at 20°C
- D.
  
  H2O (s) at 0°C
Correct Answer
A. H2O (g) at 120°C

Explanation
The sample of water in the gaseous state at 120°C has the greatest degree of disorder because the molecules are in a highly energetic and random state. In the gaseous state, the molecules have the highest amount of kinetic energy and are moving freely in all directions. This leads to a higher degree of disorder compared to the liquid or solid states, where the molecules are more closely packed and have less freedom of movement. Additionally, the higher temperature of 120°C increases the disorder further by providing more energy to the molecules.

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45.

Which pH indicates a basic solution?
- A.
  
  1
- B.
  
  5
- C.
  
  7
- D.
  
  12
Correct Answer
D. 12

Explanation
A pH of 12 indicates a basic solution. The pH scale ranges from 0 to 14, with values below 7 indicating acidity, 7 being neutral, and values above 7 indicating alkalinity or basicity. A pH of 12 is significantly above 7, indicating a strong basic solution. Basic solutions have a higher concentration of hydroxide ions (OH-) compared to hydrogen ions (H+).

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46.

Which structural formula represents 2-pentyne?
- A.
- B.
- C.
- D.
Correct Answer
D.

Explanation
The structural formula for 2-pentyne can be represented as CH3-CH2-C≡C-CH3. This molecule contains five carbon atoms in a straight chain, with a triple bond between the second and third carbon atoms. The remaining carbon atoms have single bonds with hydrogen atoms. The name "2-pentyne" indicates that the triple bond is located at the second carbon atom in the chain.

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47.

Which structural formula represents an ether?
- A.
- B.
- C.
- D.
Correct Answer
D.

Explanation
An ether is a compound that consists of an oxygen atom bonded to two alkyl or aryl groups. The structural formula that represents an ether is R-O-R', where R and R' are alkyl or aryl groups. This formula shows the oxygen atom in the middle, bonded to two different organic groups on either side.

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48.
- A.
  
  Al + 3e– → Al3+
- B.
  
  Al → Al3+ + 3e–
- C.
  
  O2 +4e– →2O2–
- D.
  
  O2 →2O2– +4e–
Correct Answer
B. Al → Al3+ + 3e–
49.
1. Based on Reference Table N, what fraction of a sample of gold-198 remains radioactive after 2.69 days?
- A.
  
  1/4
- B.
  
  1/2
- C.
  
  3/4
- D.
  
  7/8
Correct Answer
B. 1/2

Explanation
According to Reference Table N, the half-life of gold-198 is 2.69 days. This means that after 2.69 days, half of the sample will remain radioactive. Therefore, the fraction of the sample that remains radioactive after 2.69 days is 1/2.

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50.
1. As the elements of Group 1 on the Periodic Table are considered in order of increasing atomic radius, the ionization energy of each successive element generally
- A.
  
  Decreases
- B.
  
  Increases
- C.
  
  Remains the same
Correct Answer
B. Increases

Explanation
As we move from left to right across a period in the periodic table, the atomic radius generally decreases. This is because the number of protons in the nucleus increases, leading to a stronger attraction between the nucleus and the electrons. As a result, it becomes harder to remove an electron from an atom, and the ionization energy increases. Therefore, as we consider the elements of Group 1 (which are located on the left side of the periodic table) in order of increasing atomic radius, the ionization energy generally increases.

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